Electronics can be divided into a simple hierarchy consisting of devices such as integrated circuit (IC) chips, packages, printed circuit boards (PCB), and a system. The package is the interface between an electronic device, such as a computer chip, and a PCB. The devices are made from semiconductor materials, such as silicon. The IC chips can be assembled into a package, such as a quad flat pack (QFP), a pin grid array (PGA), or a ball grid array (BGA), for example using wire bonding (WB), tape automated bonding (TAB), or flip chip (FC) bumping assembly techniques. A packaged device is attached either directly to a printed wiring board or to another type of substrate, which is defined as a second level of packaging.
In BGA packaging technology, a semiconductor or IC chip is mounted on a front surface of a substrate, and a plurality of conductive elements such as solder balls are arranged in a matrix array, customarily referred to as ball grid array, on a back surface of the substrate. The ball grid array allows the semiconductor package to be bonded and electrically connected to an external PCB or other electronic devices. The BGA package may be employed in a memory component such as Dynamic Random Access Memory (DRAM) and other memory devices.
Package-on-Package (PoP) is an integrated circuit packaging technique to allow vertically combining, for example, discrete logic and memory BGA packages. Two or more packages are installed on top of one another, e.g. stacked, with a standard interface to route signals between them. This allows higher density, for example in the mobile telephone/smartphone market.